UsamaAshraf

class PostSerializer < ActiveModel::Serializer  
  attributes :id, :title, :details, :author
  def author
    object.get_author_lazily do |author|
      # Serialize the author after it has been loaded.     
      ActiveModelSerializers::SerializableResource
                             .new(author)
                             .as_json[:user]
    end
  end

UsamaAshraf

class PostSerializer < ActiveModel::Serializer  
  attributes :id, :title, :details, :author
  def author
    object.get_author_lazily
  end
end

class Post
  def get_author_lazily
    # The current post object is added to the batch here,

UsamaAshraf

posts      = Post.all
author_ids = posts.pluck(:author_id)
authors    = User.where(:_id.in => author_ids)
# Somehow pass the author objects to the post serializer and
# map them to the correct post objects. Can't imagine what 
# exactly that would look like, but probably not pretty.
render json: posts, pass_some_parameter_maybe: authors

UsamaAshraf

class PostSerializer < ActiveModel::Serializer  
  attributes :id, :title, :details, :author
  # Will run n Mongo queries for n posts being rendered.
  def author
    User.find(object.author_id)
  end
end

# This is now a Mongoid document, not an ActiveRecord model.
class User  

UsamaAshraf

class PostsController < ApplicationController  
  def index    
    # Runs a SQL join with the users table.
    posts = Post.includes(:author).all     
     
    render json: posts  
  end
end

UsamaAshraf

class PostsController < ApplicationController  
  def index    
    posts = Post.all     
     
    render json: posts  
  end
end

class Post
  belongs_to :author, class_name: 'User'

UsamaAshraf

module.exports = (user) => {
  setImmediate(() => {
    // Send a welcome email or whatever.
  });
}

UsamaAshraf

class ChatUser {
  
  displayNewMessageNotification(newMessage) {
    // Push an alert message or something.
  }
  
  // `chatroom` is an instance of EventEmitter.
  connectToChatroom(chatroom) {
    chatroom.on('message-received', this.displayNewMessageNotification);
  }

UsamaAshraf

const myEmitter = require('./my_emitter');
const sendEmailOnRegistration = require('./send_email_on_registration');
const someOtherListener = require('./some_other_listener');
const doSomethingEntirelyDifferent = require('./do_something_entirely_different');


myEmitter.on('user-registered', sendEmailOnRegistration);
myEmitter.on('user-registered', someOtherListener);

myEmitter.on('user-registered:activated', doSomethingEntirelyDifferent);

UsamaAshraf

const myEmitter = require('./my_emitter');

// Perform the registration steps

// The application should react differently if the new user has been activated instantly.
if (user.activated) {
  myEmitter.emit('user-registered:activated', user);
  
} else {
  myEmitter.emit('user-registered', user);